Going Out With A Bang: Could Algal Sex Save The Reef?

It’s no secret that the domestic situation between corals and the algae that live inside has become a little heated in recent months, but scientists may have found a way to get that steamy relationship get back on track.

First, a bit of background: The mass coral bleaching that has savaged the Great Barrier Reef over recent months occurred because of unusually warm ocean temperatures, driven by climate change and an El Nino weather system.

The bleaching starts when corals expel a type of algae that normally lives inside them, and gives them their colour. When the water becomes too warm, the algae gets all hot under the collar, and starts producing toxins that damage the corals.

That’s why the algae get turfed out. But the algae are the coral’s main source of food, so they starve, get bleached white, and are eventually overrun by a different kind of algae.

Clearly, it’s a marriage in crisis – which is why scientists have mounted an intervention.

New research published in the Journal of Molecular Biology and Evolution has revealed that the water of the Coral Sea isn’t the only thing that has been getting hot of late.

The algae appear to have responded to the conditions by starting to reproduce sexually, instead of asexually, and it turns out this promiscuity could help save the corals’ relationship with their special algae friends too.

The difference is that when the algae produce asexually they produce a more-or-less identical copy of themselves. If they produce sexually, different algae’s genetic codes get spliced together, which produces new variants of algae.

The algae that can stand the heat are less likely to get all toxic, and therefore less likely to be sent to the dog-house by the corals, which are in turn less likely to bleach. It’s a raunchy sort of survival of the fittest.

Professor Madeleine van Oppen, from the Australian Institute of Marine Science, was one of the scientists involved in the study. She said the findings are "critical in terms of developing more climate-resilient algae and corals".

The algae’s sexual reproduction was only a small part of the study. The main finding was that some algae use a mechanism to switch on genes which produce special proteins in order to protect themselves from heat exposure and mop up some of the toxic chemicals that poison their symbiotic relationship with the coral.

The sexual reproduction is important, though, because it speeds up evolution and might allow the algae to adapt quickly enough to tolerate the rise in sea temperatures.

It’s a bit of good news in a sea of bad, for those of us rooting for the Great Barrier Reef.

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